Evaluation of the effects of gold nanoparticles (AuNPs) on protein folding in Escherichia coli
Gold nanoparticles have shown promising applications, more especially in the biomedical industry. This has seen major improvements in disease diagnostics, therapeutics, imaging and treatment. All this is owed to the unique physicochemical properties possessed by the AuNPs. More studies continue to be carried out on AuNPs as the uses of these nanometer-sized particles are limitless. Water soluble citrate capped gold nanoparticles were synthesized through a slightly modified citrate method. In order to determine size, shape, dispersion and the crystalline nature of the AuNPs, characterization was done using Transmission electron microscopy (TEM) and High resolution transmission electron microscopy (HRTEM). The AuNPs were used to ascertain bacterial-nanoparticle interactions, their effect on E.coli growth as well as the effect on the solubility of E.coli proteins. The in vitro effects on DNA and protein integrity was also determined. The bacteria work was done by exposing E.coli to AuNPs. Imaging was done through TEM and bacterial growth monitored by measuring optical density at hourly intervals. AuNPs were assimilated by the bacterial cells with minimal effects on cellular integrity in DnaK- cells. DnaK + cells exhibited containment of AuNPs in the cytosol. AuNPs also inhibited E.coli growth marginally and had no observable effect on the solubility of E.coli proteins at the concentrations tested (25-75 μg/mL) in DnaK+ cells. MDH and MDH in the presence of PfHsp70 were exposed to AuNPs. The AuNPs effect was ascertained by SDS-PAGE. Citrate AuNPs managed to suppress MDH aggregation at low concentrations (2.5-25 μg/mL). At all the concentrations used, the citrate AuNPs complemented the ability of PfHsp70 in suppressing MDH aggregation. The stability of DNA exposed to AuNPs was confirmed by agarose gel electrophoresis and transformations into E.coli XL1 blue cells. DNA damage was observed at concentrations (25-100 μg/mL) after exposure for forty-eight (48) hours and for damaged DNA preparations no or fewer colony forming units were observed on agar plates. These findings show that citrate AuNPs are less cytotoxic and iii can maintain proteins in soluble form. Although their effect on protein solubility is valuable, citrate AuNPs impact on protein function and are damaging to DNA. Further studies need to be carried out in order to fine tune the physicochemical properties of these particles as a way of improving the biosafety of the AuNPs.
Networked Digital Library of Theses and Dissertations